Electric lighting.



W. W. COBLENTZ.

ELECTRIC LIGHTING.

APPLICATION .FILED suLvI. 190s.

Pafmhed Apr. 13, 19115.

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hpecruoation of Lettera Patent.

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To all whom z'tmay concern:

Be it lrnown that l, Wnmran Wham Conranura, a citizen of the United States,l and resident of Poland, county of Mahoning., State of Uhio, have invented certain new and useful lmprovements inl Electric Lighting, of which thefollowing is a' speci-` fication. v

ll/ly invention relates to a' method of and means for producing light'by .the incandescence of material traversed by electric currents.

'lhe object' of the invention is to cause the .electric current to produce a maxim amount of light with a minimum amount of heat.

centage may be materially, increased provided a solid conductor can be' secured, which under normal working conditions emits a discontinuous or banded spectrum in the infra-red. By continuous spectrum l mean that the spectral energy curve obtained by means of a prism transparent to heat rays and a heat measuring device, such as a bolometer or thermopile, is vsmooth and continuous without indentations `or 'protuberances. 'lhe infra red emission spec'- trum so obtained from a rod constructed as provided by my invention even at theV highest working temperatures is not smooth and continuous but is deeply indented, c., broken into distinct bands. 'lhis results in an increase in the amount of light emitted in proportion to the amount of heat generated.

l have discovered that numerous solid substances for example, certain oxids, carbonates, sulfates, etc., when heated to incandescence will emit discontinuous banded spectra in the infra red. Uf these, good examples for producing light are oXid of aluminum, and fluo-silicate of alum (topaz). rl`hese materials `are electrical "tl t en a solid lconductor is traversed by 'an `electric current, a relatively small Ipropornon-conductors at moderate temperature and `offer great resistance to the passage of current even at high temperature.

f @ne object of my invention is to render such substances electrically conducting so as totake advantage of the discontinuous emission spectrum.

llnother object of my invention is to pro vide incandescent bodies composed of such materials with a thread of better conducting material; for example, sodium or potas, sium aluminum silicate, which thread is joined to the more refractory and less'con ducting base, such as for example, oxid of aluminum. v

l lln order to provide such a thread of better conducting material, l may for instance, attach a rod of oxid of aluminum to the current terminals by means of sodium or potasv sium aluminum silicate melted upon the eudsof the rod and surrounding the platinum or other metallic conductor. l then place the rod in the secondary circuit of a transformer from i000 to 2000 volts having a capacity of from 100 to -300 watts, the flame from av blast lamp being allowed to play over the rod. 'lhis causes a sparlr disn charge over the glower with the volatilization of a yellow vapor from the aluminum silicate.' ln a short time a narrow streak of White light becomes visible along one side ofthe glovver `due to the deposition of some of the vapor and immediately the glower is Vrendered conductin and incandescent. 'lhe glower'is then rea y for use and for subsequentloperation is heated to a lowv red heat in any convenient manner, whereupon the streakbecomes electrically conducting and emits an intense white light, and immediately after that themain part of the glower becomes conductive to the current and incandescent.

lt is, of course, understood that in the dashing process, lines or threads of material may/be Wide bands of the same, 'almost patented-apn ia, in

covering the base of aluminum oxid.v lt is also to be understood that in the finished glower this better conducting streak is probably a chemical compound formed by the aluminum silicate and the aluminum oxid, and that it :is firmly attached to the base or'body of -aluminum oXid. v

'lhe theory of the operation of my glower is as follows: 'lhe aluminum silicate has a low melting point', but in combination with the highly refractory alumina, the melting point is raised by an unknown amount, so that the combination can be operated at a very high temperature, say from 1800 to 2000o C., Without vaporizing. The base of alumina becomes somewhat conducting at white heat and remits some light, but the most of the light is emitted by the complex aluminum silicate thread.

For the purpose of my invention in order to 4produce the non-conducting base, I' do not confine myself to alumina, but it is obvvious that I may employ other substances or I may make such substances better electrical conductors by mixing with them in a pulverized form a small amount of sodium or potassium aluminum silicate, thorium, or yttrium oxid, or any other substance suitable for increasing the conductivity, Vprovided always that the banded emission spectrum in the infra red is not seriously aifected thereby. In this case the whole glower corresponds to the fine thread of better conducting material obtained by fashing a rod of alumina in the vapors of some aluminum silicate.

In the practice of my invention I build up the base of aluminum oxid by softening particles of this material in a Oxy-hydrogen flame and gradually adding thereto until a suitable length is obtained. A glower of powdered aluminum oxid thus built up in the Oxy-hydrogen flame is very strong and homogeneous and does not shrink. For a glower of about 2 millimeter thickness and a length of about 2 centimeter-,the starting Voltage of about from 275 to 300 volts sufices and when the glower becomes 4conductive this voltage drops to about 250 volts for continuous operation. Mixtures of aluminum oxid or topaz (which is an aluminum nuo-silicate) with a few per cent. of either calcium, thorium, yttrium, etc., oxids, which lower the starting voltage and at the same time preserve the melting point of or raise it above that of aluminum oxid may be built up .in the Oxy-hydrogen flame in this general manner.

Other methods of producing the glowers may be employed. I have for instance, obtained very good results by mixing the aluminum oxid with a suitable binder and squirting it through a die by the usual methods' employed. The filament or glowei' thus obtained is then roasted to remove the blnder and shrunk into a homogeneous mass by subjecting it to extremely high temperatures.

This rod of aluminum oxid is then lashed in the vapors of an aluminum'silicate, in the manner just described, in order to deposit thereon a thread or group of threadsof the new compound which is a complex aluminum silicate.

Instead of obtaining athread o a better conducting substance upon the glower by flashing it, the alumina and the 'betterconducting substances, as, for example, an aluminum silicate or yttrium oxid may be squirted separately but simultaneously through a properly constructed die, thus obtaining a strong body of alumina with a line line of the other substance embedded in or alongside of it. This rod is then baked at high temperatures by any oi the well 7 known methods.

'lhe accompanying Figures l and 2 show a glower constructed in accordance with my invention. Fig. 3 is a diagram illustrating the distribution of energy. Fig. l shows a glower consisting of a thin thread B of the better conducting material, for example, feldsparfjoined to the more refractory and less conducting base of aluminum oxid A. Fig. L). is a cross section4 of Fig. l.

ihe principle on which my glower operates isas follows: There are two conditions to be iullilled in order to attain a high luminousl eliciency in solids which are electrically non-conducting at room temperature (20 C.) but are conducting at high temperatures (1200O to 15000) and these conditions are (l) the use oi a thin layer of a substance which can be operated near its melting point, (which melting point must be high) without evaporation and (2) as such a thin layer cannot be so operated without melting and forming an are, the combination of this.

material with a support, in such a manner that the infra red emission spectrum of the combination remains discontinuous even at the highest operating temperatures. The glower of the present invention fnllils these two conditions, inasmuch as the thin thread or lilm of better conducting material which is a new compound of unknown composition is operated near its melting point, while the main body of the glower acts as a support, and the material of that support is chosen with a view of having its emission spectrum very discontinuous and very much suppressed in the infra red. Both the .main Ioody of the glower and the lthread along its side emit a banded spectrum. yIt is to be understood that the thread is the principal source of light and that the main body is but little more than a support. Of course, it emits some light and the banded spectrum prevents it from emitting much heat, thus preventing a dissipation of energy, which then goes toward raising ,the temperature and light emission of the thread.

,It is thus possible to operate such a thread near its melting point, which cannot be done with any ordinary filament or glower, as the latter, when ity is operated so close to its melting point, sags, melts and breaks. l

In order to illustrate more clearly the physical property of the glower of my invention, I give, in Fig. 3, curve a, the distribution of energy in the spectrum which one obtains from an ordinary glower, when it is manana m highly incandescent. lln curve ll give the distribution of energy in the spectrum of a glower of my invention, when it is operated at high incandescence. llt is, of course, under-.Lood that the 'indentations in curve 'b vary somewhat with the composition of the glower. lor example, the band at about 3y. (ary-.001 m m) is owing to silicates. How-- ever, under all conditions curve b is always deeply indented.

Now, as in any ordinary -indicator diagram, such as one obtains in the expansion of steam in an engine cylinder, the area under the curve a and the horizontal axis of reference is a measure of the energy put into the glower. Similarly the area under the curve b is a measure of the energy which must be put into the glower of my invention, in order that it will emit the same amount of energy as in curve a., in the visible spectrum. 'llhe area between the curves a and b gives the amount of energy that is wasted (as useless infra red radiations not a'ecting the eye) in a glower of typen when it emitsI the same amount ofenergy in the visible spectrum as does a'glower of ymy invention.

The processes set forth above in the preparation of the glower cause the latter to have certain physical characteristics, that is, `V a marked banded emission spectrum in the infra red which isnot possible to obtain by methods heretofore described.

l claim as my invention:

1. The process for the` manufacture ofv glowers for incandescent lamps, which consists in providing a rod of aluminum oxid with terminals of aluminum silicate and allowing an electrical spark discharge to take' place between the terminals. 4

2. rlhe process for the manufacture of glowers for incandescent lamps, which consists in providin a rod of aluminum oxid with terminals o an alkali metal aluminum silicate and allowing an electrical discharge in providing a rod of aluminumoxid with terminals of aluminum silicate and allowing an electrical discharge to take place between said terminals for the purpose of forming a layer of the new compound substantially as described.

,5. rllhe process for the manufacture of complex aluminum silicates by passing an electric discharge over the rod of aluminum oxid, in a vapor of aluminum silicate for the purpose of forming a layer of the new compound upon the rod of aluminum oxid.

6. Al glower for incandescent electric lamps consistin of a main body of aluminum oxid an a thin band of a compound composed of aluminum silicate and aluminum oxid. l

7. A glower for. incandescent electric lamps consisting of a compound of aluminum oxid and aluminum silicate.

8. A glower for incandescent electric lamps consisting of a compound of aluminum oxid and an alkali metal aluminum silicate.

sisting of a compound of aluminum oxid and potassium aluminum silicate.

10. A glower for electric' lighting 'appa- 9. A glower` for incandescent lamps con-I ratus composed of a main body of aluminum oxid and a thread of complex aluminum silicate attached thereto, the combination having the physical property of emitting a banded spectrum kin the infra red, when heated to or above 1800 to 2000 degrees centigrade. ,f

11. A glower for incandescent lamps composed of complex' aluminum silicate, which has the physical property of lemitting a banded spectrum in the infra red when heated above 1800 degrees centigrade'.

12. As a new article of manufacture, a glower composed of second class conductors having the physical property ofl emitting a banded spectrum in the infra red, at or above 1800 de rees centigrade.

Signed at ashington in the District of Columbia this seventh day of July A. D. 1908.

l/VILLllAM WEBER COBLENTZ.

Witnesses:

FLORA RAYMOND', L. L. BOYD. 

